1. 1 Review Projections etc. & data types & Downloading or HOW TO GET CONFUSED

2. 2 Overview Review of Projections –How to do Difference between Define and Project –Scale Data Types –GeoDatabase- orthophotos –Coverage- images –Shapefile Downloading

3. 3 Overview Review of Projections –How to do Difference between Define and Project –Scale Data Types –GeoDatabase- orthophotos –Coverage- images –Shapefile Downloading

4. 4 Syracuse  On the Sphere

5. 5 On the Flat Map -76.19, 43.07 Extents

6. 6 X, Y = Longitude, Latitude Lines of constant Longitude Lines of constant Latitude 0-90+90-180+180 0 -30 30 -90 90 -60 60 Equator Stretch the top Stretch the bottom

7. 7 X, Y = Longitude, Latitude Lines of constant Longitude Lines of constant Latitude 0-90+90-180+180 0 -30 30 -90 90 -60 60 Equator 90E, 30N 90W, 30S +90, +30 -90 -30 W76.15° N43.04°-76.12° 43.08°

8. 8 Projection data The.xml file is the metadata file you see in Catalog ArcGIS does NOT “see” the.xml file It sees the.prj file

9. 9 Xml vs. prj The xml file is created from the prj It is a one way connection In general, the extent of the file will not change when you change its projection

10. 10 Projecting Two Cases and Two Tools –Data has a.prj Then you can project it to another one Project –Coverages are different than features –One tool for each –Data does not have a.prj Then you must DEFINE PROJECTION Again, two tools

11. 11

12. 12 Only if working with COVERAGES!!

13. 13 So Use Project if the data has a.prj Use Define Project if the does not have a.prj Make sure you are working with the correct tools for coverages and features If wrong tool won’t display your data!

14. 14 Last little booby trap Geographic SCALE

15. 15 Not lining up? Obviously data that is not in the same projection/datum is not going to line up if there is no.prj file Data of different scale, even if the same projection and datum, may not line up very well

16. 16 Scale Problems Remember that scale is related to data accuracy –1/25k is + or - ~40 feet –1/100k is + or - ~ 80 feet –Etc. Also have generalization

17. 17 Overview Review of Projections –How to do Difference between Define and Project –Scale Data Types –GeoDatabase- orthophotos –Coverage- images –Shapefile Downloading

18. 18 Coverages Oldest data structure (see book) Are folders so have to move the entire cover folder (PC) If the cover is in a folder that has a INFO folder then it is a Workstation cover and you have to move the entire containing folder

19. 19 Shapefiles A simpler structure than coverages Like drawing Lines between polys are duplicated (they are NOT in a coverage) By themselves shapes are single precision In a GeoDatabase they can be double precision

20. 20 GeoTiffs Raster images (graphics) Geo means they know where they belong is space Tif means that they are Tif images Used most often for images of quad sheets and other dumb maps

21. 21 Images & orthophotos Images –Usually satellite images –Also know where they belong Orthophotos –Aerial photographs –Rectified so are geographically correct –High resolution now available (2 ft)

22. 22 Grids DEM or digital elevation models Usually of continuous surfaces Like images and orthophotos they know where they belong

23. 23 GeoDatabases The latest whiz-bang structure from the gnomes at ESRI Are containers for data All of the types we have discussed Deal with all the data at the same time Allow interlayer topology

24. 24 This week You will be downloading many of the data types we have discussed And one more - the exchange file –E00 files –Text versions of coverages –So you have to import them (tool) –And you will probably want to convert them to shapefiles

25. 25 Overview Review of Projections –How to do Difference between Define and Project –Scale Data Types –GeoDatabase- orthophotos –Coverage- images –Shapefile Downloading

26. 26 Downloading There are lots of data sites Some are easy, some are not Stay away from the National Map See my GIS Links page

27. 27 Summary Coverages Shapefiles Grids GeoTifs Images Orthophotos GeoDatabase